1. Field of the Invention
The present invention relates to a semiconductor photoelectric converting device, more particularly relates to a semiconductor photoelectric converting device as an infrared light receiving element.
2. Description of the Related Art
An infrared detector for use in an infrared type imaging system can be classified into a photon detector using a semiconductor in principle, a pyroelectric type detector utilizing a pyroelectric effect and a Seebeck type detector utilizing a Seeback effect.
As the photon detector, a structure as shown, for example, in FIG. 1 is known in which it includes a charge transfer substrate unit 3 having charge transfer elements in its silicon substrate 1, a light-receiving substrate unit 7 having a p type HgCdTe layer 5 and n type HgCdTe regions 6 in its CdZnTe substrate 4, and indium metal posts 8 by which the charge transfer substrate unit 3 is electrically connected to the light-receiving substrate unit.
When the conventional photon detector having an arrangement as set out above is brought to a temperature in proximity to room temperature so that it may detect radiation in the neighborhood of room temperature, then electric charges developed due to heat evolved in the detector itself will be mixed, as noise, with those electric charges created due to heat from an infrared radiation containing object information because a band gap in the materials constituting the detector is as small as about 0.12 eV. In the conventional photon detector, therefore, it is not possible to accurately detect any infrared radiation other than that of high output power as in a CO.sub.2 gas laser and hence to obtain a clear-cut image in an imaging system utilizing it. In the imaging system utilizing the conventional photon detector, a cooling system such as a Joule Thomson type cooling unit and Stirling cycle type cooling unit is provided to cool it to about the liquid nitrogen temperature (absolute temperature 77 K.). By doing so it is possible to detect the infrared radiation with high sensitivity. A resultant imaging system becomes bulkier and higher in manufacturing costs and is restricted to the application of a defense equipment as well as a space equipment.
Further, the pyroelectric type detector is adapted to convert infrared radiation to an electric signal but it is lower in sensitivity. The Seebeck type detector converts infrared radiation to heat and the heat to an electric signal, but its response speed is slow.